1. Field of the Invention
The present invention relates to a circular drill cutter with indexable bits and associated bit seats for producing pockets, elongate slotted holes, through-bores in a solid material, with a possibility of relief milling and rearward counterboring, reaming of already produced openings, wherein the tool is rotatably driven on CNC-controlled machine-tool and is displaced along a path with a continuous feeding along a Z-axis or, during formation of large pockets and during copy milling, is driven without feeding along the Z-axis, wherein the indexable bit has, for each cutting engagement region, a main face cutting edge and a face side cutting edge, a finishing cutting region, and a cross-cutting edge which forms a transitional region between finishing cutting region and the adjacent cutting engagement region, and a cross-cutting edge which forms a transitional region between the main face cutting region and the next cutting engagement region, and wherein the indexable bit has a chip forming groove.
2. Description of the Related Art
German Publication DE 4 342 577 A1 discloses a drill cutter for producing openings, fits in a solid material, cut-out, and threads in association with CNC-controlled machine-tools. In DE 4 342 577 A1, the outer flank cutting edges are divided in a roughing cutting region and a finishing cutting region. In German Patent DE 39 09 77, two front cutting edges per a cutting unit are used for forming cored openings. In order to provide two end sides for each indexable bit, in DE 39 09 077, respectively, two triangularly shaped indexing bits are used. The drawback of this consists in that the necessity to provide, respectively, two indexable bits for each cutting unit, permits mounting on the tool shank only a limited number (a half) of cutting units. The necessity to provide two bits for each cutting unit double the price of a cutting unit and, secondly, the fitting of the milling cutter within the limited number of the cutting units increases the production time by 100%. Further, a method of producing fits is disclosed in DE 43 42 577 A1 in which the finishing size is produced during the return stroke. However, this cutting geometry and this method do not permit to produce fits in a solid material without changing the tool.
Despite these improvements, in many cases, an economical use is not possible. For one, when cutters are formed as indexable bits, they can be turned only once, secondly, in many cases such as the production of pockets during copy milling and milling off burned spots and cored recesses, the second inwardly located face cutting edge is not necessary.
Also, during the production of the through-bores, the inwardly located face cutting edge must not necessarily lie at the same height. Still further, a non-slip mounting of the indexable bits on the bit holder in accordance with the solution set forth in DE 43 42 527 A1 (recesses and tubes) is not insured during heavy machining. Yet further, the space provided for the necessary key elements (torque screwdriver) for changing the bits limits the number of indexable bits to be secured on the tool head with screw clamps. In addition, the possibility of chambering and relief milling need be insured.
Therefore, an object of the present invention is an economically operating circular drill cutter with indexable bits capable of being turned more than once, with an improved roughing cutting region, with an integrated finishing cutting region, and with a cutting edge for rearward chambering of through-openings with which relief milling of recesses is also possible, and with drill cutter having a slip-free bit seat, and wherein a largest possible number of indexable bits with different face cutting edges can be secured on the circular drill cutter.